A compaction assistance system is proving its worth in Staffordshire, as Margo Cole reports.
The slow uptake of machine control and automatic measurement systems in the UK - particularly in comparison with their popularity elsewhere in Europe - has been attributed to a range of factors, including the naturally conservative nature of our engineers, the way contracts are set up, the additional cost of these technologies, their complexity and the volume of construction equipment that is hired rather than contractor-owned.
Whether these factors are real or merely perceived barriers, they can be overcome, as evidenced by the successful adoption in Staffordshire of a system that helps roller drivers achieve the right level of compaction on paving jobs.
“Surfacing is an expensive operation,” explains Peter Boulton, operations manager for Enterprise, which has a five year asset management contract with Staffordshire County Council . “If we can get it right first time we’re going to save a lot of money in the long term. This technology helps enormously,” he adds. “At the end of day it’s down to the guy on the ground to do it right - you can’t stand over them all day long. This information helps them feel part of it.”
The “information” he refers to is provided by the Moba MCA-2000 Compaction Assistant, which is fitted inside the cab of the roller. It gives the operator a continuous, real-time visualisation of the surface as it is compacted, which makes it easy for the operator to see how many passes they have achieved on each section of the carriageway.
The system can be pre-programmed with the required number of passes, and the image changes colour when this number has been reached, so the operator knows when to stop. It also displays the temperature of the paved asphalt, so the roller operator can make sure they compact within the optimum temperature range.
If we can get surfacing right first time we’re going to save a lot of money in the long term. This technology helps enormously
Peter Boulton, Enterprise
According to Enterprise surfacing manager Chris Fowler, the system has enabled its operators to “take ownership of” their work. “Compaction is critical to making the road last longer - and this tool helps the operator achieve that quite easily,” he says. “But if any issues are highlighted, we know where to go to.”
The operators are not left entirely to their own devices: Staffordshire County Council laboratory testing manager Phil Cartmail makes sure random coring is done, and the site teams have a density meter with them to check they are achieving the required compaction levels. But at a time when local authorities budgets are stretched, Cartmail says the system gives him peace of mind.
“The lab has limited resources, so we have to work out where the risks are,” he explains. “Compaction is a massively important thing. If we can control the temperature and can confirm that the right number of passes has been carried out, that has to be the way.”
At the start of each job, the team “rolls to reference” to calculate how many passes are needed to achieve the required density at each location. This can vary considerably - especially for surfacing contracts, where a new layer of blacktop is going down on an existing pavement.
“Most of the carriageways are evolved roads, and there’s no guarantee of what’s underneath,” explains Boulton.
The information is fed back into the MCA-2000, which uses GPS to identify the roller’s location on the road and match this with the design requirements at the various sections along the route.
One of the system’s selling points for Enterprise and Staffordshire County Council was its simplicity, according to Fowler. “It’s an easy process,” he says. “It gives the operator a good chance of doing a good job on his own. They want to do a good job, but there wasn’t the information to allow them to do that.”
“There is a simplicity about this system that helps with the guys on the ground,” adds Boulton, who says he looked at other, more sophisticated, alternatives before opting for the MCA-2000.
The equipment was supplied by Clee Hill Plant, the UK’s largest supplier of compaction equipment, which signed a distribution deal with Moba last year. Clee Hill managing director David Hargreaves also liked the system’s simplicity.
“Unless you get the operator to buy into it, you’re on a hiding to nothing,” he says. “So it makes sense to start with something as simple as possible. Then you will get buy-in.”
Clee Hill has taken five MCA-200s so far for its roller fleet, and they have already been used by a variety of contractors, including Tarmac, Aggregate Industries and Eurovia.
Enterprise has taken one system, fitted to a Hamm HD90 twin drum vibration roller. The machine arrived in Staffordshire last autumn, after a trial period, and is being used by two paving crews on a wide range of surfacing jobs from single track rural roads to dual carriageways.
“When we’re paving it’s working,” says Cartmail. “It is being used for everything that goes through the paver.”
Not surprisingly, there is a premium on hiring a roller fitted with the compaction assistant, but both Enterprise and Staffordshire County Council believe the higher price tag is worth it. “Clearly there’s a cost to this - the machine without this system will be cheaper than the one with it,” says Boulton.
“We’ve taken the decision that we want to pay a bit extra to use this [equipment]. There is such an obvious advantage to having this available that - within reason - we will pay extra for it.”
Boulton says the relationship between client and contractor - which he describes as a “virtual joint venture” - has allowed them to be “a bit more adventurous” when it comes to innovative techniques and technologies, but adds: “It still has to be cost effective.
Unless you get the operator to buy into it, you’re on a hiding to nothing, so it makes sense to start with something as simple as possible
David Hargreaves, Clee Hill
“The nature of the contract gives us the opportunity to try lots of things,” he says, citing high levels of recycling as an example, as well as trials with different pavement construction materials, like HBM and foam mix.
Enterprise’s contract is worth about £50M a year, and runs until 2014.
Boulton explains that it is a “quality driven contract - driven by KPIs, not a schedule of rates,” and says it has “evolved over time with some fairly open-minded people” to reach the current “virtual joint venture” situation.
That open-mindedness may be a clue to why client and contractor have both responded so positively to the compaction assistance system, and why they are now looking at what more they can do with it.
“The first thing we were looking for was to make life easier for the operator and site staff,” explains Fowler. “Now that we’ve got confidence in our operators, we can carry on with rest of the process.”
He says the next stage is to do more with the records that the system provides, and then look at potential add-ons, such as a sensor that records when the roller is in vibration mode and when it is not. Another option that the Staffordshire team is interested in is fitting the system to the smaller rollers that are used by patching gangs.
And Cartmail points out that developers could use the system to prove that they’ve achieved the required compaction specification for roads that will later be adopted by the local authority.
For now, though, the team is happy that the system is doing what they brought it in to do - giving them confidence that the required level of compaction is being achieved on maintenance jobs throughout the county.
“I think it’s the way forward,” says Fowler. “I’m less worried about having carriageways fail because of lack of density.”